Rubber curing bladders having self release or low adhesion to curing or cured hydrocarbon rubbers

ABSTRACT

Hydrocarbon polymers with grafts of polyethers, polylactones, or polyesters from the reaction of phosgene with glycols having from 1 to 4 carbon atoms are disclosed as having good release properties or low adhesion to hydrocarbon rubber materials. The hydrocarbon backbone polymers include EPDM, hydrogenated polybutadiene, and hydrogenated poly(styrene-butadiene) all said polymers having pendant succinic anhydride groups or brominated p-methylstyrene-isobutylene copolymers. The above-referenced graft copolymers along with butadiene-acrylonitrile rubber or epichlorohydrin polymers or copolymers are described as useful polymers to make self-release curing bladders or sleeves for use in making molded articles such as pneumatic tires.

CROSS-REFERENCE

This is a division of application Ser. No. 08/222,154, filed on Apr. 4,1994, of Daniel F. Graves et al. for RUBBER CURING BLADDERS HAVING SELFRELEASE OR LOW ADHESION TO CURING OR CURED HYDROCARBON RUBBERS, now U.S.Pat. No. 5,385,459, which is a CIP of Ser. No. 07,906,095, filed on Jun.29, 1992, of Daniel F. Graves et al., now abandoned.

FIELD OF INVENTION

Polymers useful in making curing bladders or sleeves (used primarily tomanufacture (more specifically cure or vulcanize) pneumatic tires) aredescribed. These polymers must have good heat stability and physicalproperties such that they can be inflated during use and not rupture.The polymers described are butadiene acrylonitrile copolymers,epichlorohydrin polymers and copolymers, and graft copolymers. The graftcopolymers have backbones of brominated p-methylstyrene-isobutylenecopolymer, ethylene-propylene terpolymer, substantially hydrogenatedpolybutadiene, and/or substantially hydrogenated styrene-butadienerubber. The grafts are various polyethers, polyesters from cycliclactones, and polycarbonates made from phosgene and glycols. Thesepolymers when used in a curing bladder formulation reduce or eliminatethe need for a release agent to prevent adherence of the bladder to thecured tire.

BACKGROUND

Inflatable rubber bladders are used in machines for assembling, formingand curing pneumatic tires. These bladders are typically made fromisobutylene rubbers especially when used at higher temperatures such asfrom 100° to 150° C. Isobutylene polymers are preferred over diene basedpolymers because they are inherently more resistant to oxidation at theabove-recited cure temperatures typically used and often required forforming tires. This is because of the relatively low levels residualunsaturation available for crosslinking in isobutylene polymers (butylrubber) compared to diene-based polymers. Adhesion of the cured tires tothe rubber bladders is generally avoided by applying a liquidsilicone-based lubricant either to the bladder or the tire componentsthat are to be in contact with the bladder.

The need to apply a lubricant (also called dope) to the bladder tireinterface slows the tire manufacturing process. Lubricants as usedherein define liquids that do not crosslink under the conditions used tocure tires (i.e., 100°-180° C.). Excessive lubricant or the transfer oflubricant can discolor the tires or contaminate other surfaces wherebonding is desired. Insufficient lubricant results in bonding of thebladder to the tire at the tire-bladder interface. When this interfacebond is broken or torn when removing the cured tire, this can causedefects in the tire, roughens the bladder surface, or can promotebladder failure.

Bladders are used in curing presses to press the tread and sidewallregions of the tire outwardly against the mold surface during tiremanufacturing. These bladders are filled with a heated fluid (preferablysteam) to help speed the curing process of the tire. The high potentialelongation of the bladder or sleeve (i.e. greater than 300 percent)allows the bladder to stretch and conform during tire curing and allowsthe bladder to stretch while tearing away from the molded tire.

Other inflatable bladders and sleeves have found uses in other rubberforming and curing processes. These similarly suffer from the necessityof supplying a lubricant at the interface between the bladder and thehydrocarbon component to be cured.

SUMMARY OF THE INVENTION

Polymers and molded polymer compositions are described having reducednatural adhesion (non-stick characteristics) to tire compounds, butylrubber inner-liners, and other hydrocarbon polymer compositions.Inflatable monolayer membrane curing bladders made from these polymersrequire less interface lubricant or can be used without interfacelubricant when used in molding and curing (e.g., vulcanization) ofhydrocarbon polymer compositions such as pneumatic tires. These polymersdisclosed herein have good release properties from curing rubbercompositions (e.g. isobutylene polymer based tire innerliners) and thuscan be monolayer membranes rather than laminates as sometimes taught inthe prior art. The polymers used to make the bladders have polarcomponents in the backbone or have polar grafts that contribute to thistendency to not adhere to the hydrocarbon polymers.

DETAILED DESCRIPTION OF THE INVENTION

Several polymers and graft copolymers have been developed that have thephysical properties required of an inflatable bladder or sleeve for usein curing rubber (e.g., tires) and show the unique property of little orno adhesion to a typical cured hydrocarbon based polymer when saidhydrocarbon-based polymer is cured in contact with the bladder or sleevematerial. The polymers have polar type monomers in the backbone orgrafted to the backbone which impart to the rubber compound a tendencynot to adhere to hydrocarbon polymers.

The bladders or sleeves of this invention are desirably monolayermembranes (i.e. the exterior surfaces and the bulk of the bladder areessentially the same composition). As is common to the curing bladderart, one can apply nonbonding liquid lubricants to the surfaces of thebladder, but these are not required for the effective release of thebladder or sleeve surface from the cured hydrocarbon rubber composition.Thus, desirably, the bladder or sleeves of this invention do not havecrosslinked surfaces of polysiloxanes or polyurethanes, or the like.Crosslinked is used to define polymers which are chemically bondedtogether with similar molecules or with the bladder or sleeve substratecomposition such that chemical bonds need to be broken to remove thecomposition from the surface of the bladder or sleeve.

Graft copolymers whose backbone is isobutylene copolymers with at leastpara-methylstyrene are advantageously used for this application.Desirably, these copolymers are made without using optional dienemonomers of 4 to 8 carbon atoms. These polymers are desirably highaverage molecular weight such as from about 75,000 and up, desirablyfrom about 75,000 to about 2,000,000, and preferably from about 100,000to about 500,000. These copolymers can be brominated by free radicalbromination reactions which results in the selective replacement of thehydrogens on the para-methyl group of para-methylstyrene by a bromineatom. During the bromination reaction, the weight percent brominedeveloped in the polymer for this application is from about 0.1 to about17, desirably from about 0.2 to about 8.0 and preferably about 0.5 toabout 2.5 percent.

The weight percent of para-methylstyrene in the backbone for thisapplication is about 0.1 percent by weight to about 30 percent byweight, desirably from about 1 weight percent to about 25 weightpercent, and preferably about 2 weight percent to about 20 weightpercent of the copolymer of isobutylene and p-methylstyrene. Increasingamounts of para-methylstyrene in the copolymer increases its modulus andTg. The bromination of the para-methyl group creates a grafting site onthe backbone and also serves as a crosslinking site. The amount ofp-methylstyrene can be varied independently from the amount ofbromination of said methyl group as long as the total replaceablebromine atoms on the backbone are sufficient for grafting andcrosslinking. These polymers are commercially available from Exxon asXP-50 in their brominated form.

Said copolymers of isobutylene and p-methylstyrene are cationicallypolymerized by Exxon. The r₁ value for isobutylene is reported as 1,while the r₂ value for p-methylstyrene is reported as approximately 1.4.Thus, procedures for isobutylene polymerizations can be easily modifiedto produce copolymers. Slurry copolymerizations are also reported forthis copolymer system. Radical bromination creates the brominated formof the isobutylene-p-methylstyrene copolymer. The bromination isreported to occur in solid phase, slurries, or solutions.

The polar polymers reacted with and desirably grafted onto thebrominated para-methylstyrene isobutylene copolymer-or later specifiedmaleic anhydride modified polymers can be any alkylene-oxide polymer(polyethers) or polyether copolymers having from 1 to 4 carbon atoms perrepeat unit; or polycarbonates made from phosgene and glycols having 1to 4 carbon atoms per glycol; or polyesters from ring openingpolymerizations of cyclic lactones having from 4 to 5 carbon atoms perrepeat unit. The average molecular weight of said polar polymers beforegrafting can be from about 100 to about 20,000, desirably about 200 toabout 15,000, and preferably from 400-5,000. Polyether polymers andcopolymers can be made from ethylene oxide, propylene oxide,tetrahydrofuran, etc. The polar polymers used for grafts can be branchedor linear, but linear polymers are preferred. The polar polymers can beblended by type or by molecular weight. The alkyleneoxide polymers canbe of one molecular weight or blends of different alkylene oxides or ofdifferent molecular weights or both. The polymers can have multiplechain ends reactive with the brominated para-methyl-styrene but polymerswith a single chain end capable of grafting to the backbone polymer arepreferred. The chain ends reactive with the para-methylstyrene aredesirably hydroxyl groups.

The reaction and grafting of thebrominated-para-methylstyrene-isobutylene with the polar polymers can beaccomplished by melt blending the two polymers in the presence of acidscavengers such as oxides, carbonates, and hydroxides of Mg, Zn, Ca, andBa. The reaction and grafting of said polar polymers throughnucleophilic substitution of the polar polymer chain end for the bromogroup of the methylstyrene can desirably be conducted in a Banbury orother mixer at temperatures from about 50° C. to about 180° C., andpreferably from about 100° C. to about 150° C. The other compoundingingredients for a rubber compound can be added simultaneously withgrafting of polar polymers or as a separate step.

The amount of polar polymers reacted and potentially grafted is fromabout 2 to about 50 or 100, desirably from about 5 to about 30, andpreferably from about 10 to about 20 parts by weight based on 100 partsby weight of the brominated p-methylstyrene-isobutylene copolymer andthe polar polymers. The rubbers compounded into a molded article can bea blend of said reaction product of the brominatedp-methylstyrene-isobutylene copolymer and polar polymers (graftedcopolymer) and regular brominated p-methylstyrene-isobutylene copolymer,EPDM, and other polymers such that from about 5 to about 100 weightpercent of this rubber is graft copolymer, and desirably about 5 toabout 35 percent of the rubber is graft copolymer. The brominatedp-methylstyrene-iso-butylene copolymer, EPDM, hydrogenatedpolybutadiene, or hydrogenated SBR polymers can be used from 0 to about95 weight percent, and desirably from about 65 to about 95 weightpercent of the rubbers used to make molded articles. Thus, the moldedarticle can be from 2 to about 40, desirably from about 5 to about 30weight percent, and preferably about 10 to about 20 weight percent ofsaid polar polymers based on all the rubbers used in the composition.

Another suitable polymer backbone for this invention isethylene-propylene-diene copolymers (EPDM) (also known asethylene-propylene terpolymer). These are well known to the art and arefrom about 30 to about 80, and desirably from about 50 to about 75weight percent ethylene. The second monomer can be any alpha unsaturatedmonoolefin of 3 to 12 carbon atoms with propylene being the preferredmonomer. The weight percent of said alpha unsaturated monoolefin in thecopolymer is from about 20 to about 70 and desirably about 25 to about50. The diene is a nonconjugated diene having from about 6 to about 12carbon atoms. Examples of dienes are dicyclopentadiene, 1,4-hexadiene,and ethylidene norbornene.

The weight percent unsaturation from diene in said EPDM is about 0.1 toabout 10, desirably about 0.2 to about 5.0, and preferably about 0.4 toabout 2.5. The molecular weight of the EPDM is from about 75,000 toabout 500,000 and desirably from about 150,000 to about 400,000.Alternatively, a blend of EPDM polymers of different molecular weightscan be used.

Another suitable polymer backbone for this invention is polybutadiene(PBD) or poly (styrene-butadiene) copolymer (SBR) that have beenhydrogenated to remove from about 90 to about 99.5 percent and desirably95-99.5 percent of the backbone unsaturation. The average molecularweight of these polymers is from about 75,000 to about 500,000, anddesirably from about 150,000 to about 400,000. The mole ratio of styreneto butadiene in the SBR can vary from about 1:50 to about 1:1. Thesepolymers may contain minor amounts (less than 10, 20, or 30 mole %) ofother unsaturated copolymerizable comonomers having 2 to 18 carbon atomsand heteroatoms of oxygen, nitrogen, and hydrogen. The wordshydrogenated SBR or hydrogenated polybutadiene will be used to representthese substantially (e.g. greater than 70, 80, 90 and 95 percent)hydrogenated polymers in this specification.

The EPDM, hydrogenated polybutadiene and hydrogenated SBR backbones forthis invention are modified by reacting maleic anhydride with theunsaturation in the polymers. This reaction of maleic anhydride with amonomeric olefin is well known to organic chemistry as the "Ene"synthesis or reaction. Further information on this reaction is instandard textbooks such as J. March, Advanced Organic Chemistry 3rd Ed,John Wiley & Sons: New York, p. 711. This reaction creates succinicanhydride pendant groups on the polymer backbone. The amount of maleicanhydride reacted with the various polymer backbones can be from about 1to 50, desirably from about 1 to about 20, and preferably from about 2to about 10 parts by weight per one hundred parts of backbone rubber.

Similar functionalized polymers to the polymers modified with maleicanhydride through the "Ene" reaction are hydrogenated polymers ofpolybutadiene, said EPDM or said hydrogenated poly (styrene-butadiene)(SBR) modified with maleic anhydride in the presence of free radicalsources. These reactions are conventionally done in hydrocarbon solventsat 50°-180° C. for 0.1 to 24 hours using from about 0.01 to about 5parts by weight free radical initiators per 100 parts rubber. The amountof maleic anhydride can be from about 1 to about 100, desirably fromabout 1 to about 20, and preferably from about 2 to about 10 parts byweight per 100 parts by weight rubber. The free radical sources are thefree radical initiators of peroxides, azo initiators, persulfates, andthe like.

These polymers modified using free radical initiators with maleicanhydride can be used interchangeably for the products of the "Ene"reaction mentioned above to serve as a backbone for grafting reactionswith the polar polymers already described. The reaction with maleicanhydride creates grafts of pendant anhydrides from the polymer backbonethat can serve as the grafting site for the esterification with thepolar polymer end groups. One such material made is from an EPDMbackbone is available commercially from Uniroyal as Royaltuf™ 465.

The polar polymers previously described as material to be grafted to thebrominated-para-methyl-styrene-isobutylene backbone can be used with theabove products of the "Ene" reaction or maleic anhydride modifiedpolymers of hydrogenated polybutadiene, hydrogenated SBR, or EPDM. Thegrafting of the polar polymers to the backbone polymers are conducted bymelt blending the backbone polymers with the polar polymers at 90° to220° C., desirably from about 110° to about 180° C. and preferably fromabout 120° to about 160° C. for times from 1 minutes and longer,preferably from about 2 minutes to about 10 minutes. In this process,the anhydride groups created by the grafting of maleic anhydride ontothe polymer backbone reacts with the hydroxyl group of the polarpolymers forming an ester linkage. The composition of the graftedcopolymers from EPDM, hydrogenated polybutadiene, or hydrogenated SBR bythe "Ene" process or free radical source plus maleic anhydride processare from about 2 to about 50, desirably about 5 to about 30, andpreferably about 10 to about 20 weight percent polar polymers which aregrafted onto the rubbery backbone. The polar polymers may be used inamounts from about 2 to about 100 parts by weight per 100 parts byweight of said ethylene-propylene terpolymer or substantiallyhydrogenated polybutadiene, or substantially hydrogenatedstyrene-butadiene copolymer rubber.

The rubbers compounded into stocks for making molded rubber articlesneed not be 100 percent of said polymers grafted with polar polymers.The grafted copolymer can be from about 2 percent to about 100 percent,desirably about 5 to about 25 weight percent of the rubber in the stock.EPDM or hydrogenated polybutadiene or hydrogenated SBR can be up to 98weight percent and desirably from about 75 to about 95 weight percent ofthe rubber in a molded article. The molded article can be have fromabout 2 to about 40, and desirably from about 5 to about 30 weightpercent and preferably about 10 to about 20 weight percent of said polarpolymers based on all the rubbers used in the composition.

Another group of suitable polymers useful in this invention are thevarious epichlorohydrin elastomers. Such materials can desirably be ahomopolymer of epichlorohydrin or a copolymer with ethylene oxide, allylglycidyl ether or both. The amount of ethylene oxide in these copolymerscan desirably vary from about 1 to about 35 weight percent and desirablyfrom about 3 to about 30 weight percent. The amount of allyl glycidylether can be from about 1 to about 5 weight percent of the copolymer.The amount of epichlorohydrin can vary from about 63 to about 99 weightpercent of the copolymer. These polymers are made from by cationic,coordination polymerization mechanisms and commercially available fromHercules, Inc.; Osaka Sada Co., Ltd.; and Nippon Zeon Co., Ltd. Theaverage molecular weights useful for this application are from about50,000 to about 500,000, desirably about 80,000 to about 250,000. Thesepolymers have reduced adhesion to hydrocarbon rubber compositions.

Another group of suitable polymers useful for this invention isbutadiene-acrylonitrile copolymers. These copolymers can be made by avariety of polymerization methods, but free radical emulsion polymerizedpolymers are preferred. The weight percent acrylonitrile in thesecopolymers is from about 18 to about 55, desirably about 25 to about 45,and preferably about 30 to about 40, with the residual being butadieneor blends of butadiene and optional monomers. Optional monomers aredesirably present at less than 2, 10, 20 or 30 mole percent of all themonomers present. The optional monomers have at least one unsaturatedcarbon to carbon bond from 3 to 15 carbon atoms, and other atoms such ashydrogen, oxygen, and nitrogen, and optionally contain a second doublebond or an aromatic ring. Butadiene-acrylonitrile heat stability isimproved with a special antioxidant heat stabilizers such as the zincsalt of 2-mercaptobenzothiazole (Zetax) to keep the polymer fromdegrading at the use temperature. Such compounds are used at theconcentration of 0.25 to about 2 parts per 100 parts by weighthydrocarbon rubber. The average molecular weight of the polymer for thisinvention is from about 50,000 to about 500,000, and desirably is fromabout 80,000 to about 250,000.

To be useful as curing bladders, all the above referenced polymers andgraft copolymers must be formulated into rubber compounds with goodelasticity, high strength, and good property retention after aging oruse at high temperatures such as 100° C. to about 150° C. Thus thephysical properties as recited below desirably are retained for at least24 hours, 48 hours, 1 week, or one month at temperatures of 100°, 120°,135°, or 150° C. Typical formulations for these compounds are well knownto the art. High structure reinforcing carbon blacks are used in thisinvention to give higher modulus and better abrasion resistance. Thesecarbon blacks are desirably high structure blacks having calculatedultimate particle sizes from about 20 to about 40 nanometer diameter andIodine Numbers by ASTM methods of about 60 to about 160 mg/g. Oils areused to extend the polymers. These oils can be paraffinic, naphthenic,or aromatic. Antioxidants are used to prevent oxidative crosslinking orchain degradation of the polymers. The antioxidants effective in thesecompositions include paraphenylenediamines, hindered phenols, andpolymerized quinolines. Commercial EPDM, hydrogenated SBR, brominatedp-methylstyrene-isobutylene, SAN/EPDM blends or grafts, and hydrogenatedPBD polymers can be blended with the polymers and copolymers of thisinvention. EPDM and the hydrogenated rubbers generally gives acomposition higher resistance to oxidation in that these polymers havelow residual unsaturation in the polymer backbone. Accelerators andcuratives will be discussed individually for each of the graftcopolymers or polymers.

The compounds are formulated to give an ultimate tensile strength of1500 psi or more, a 300 percent modulus value of 500 to 1000 psi, aShore A hardness of about 55 to about 70, and desirably of about 60 toabout 65. These physical properties are required of the bladder orsleeve when installed in a curing press, and they are desirably retainedduring the useful life of the bladder or sleeve. Thus, when the bladderor sleeve degrades so these properties are not met, the bladder orsleeve is replaced. Depending on the Size and shape of the bladder orsleeve, these tests may be performed on specimens cut from the bladderor sleeve, or when that is not possible, one would cure the sameformulation used to make the bladder or sleeve under identicalconditions as a flat sheet and test the flat sheet. It is also desirablethat the tear strength at 170° C. be in excess of 100 psi and moredesirably in excess of 200 psi.

The brominated para methylstyrene isobutylene copolymers reacted andgrafted with polar polymers are cured with phenolic resins, sulfur,sulfur donor compounds, ZnO, and other resins reacting through thebrominated methyl group on the methylstyrene. Sulfur donors arecompounds like di-morpholino disulfide or dipentamethylenethiuramhexasulfide which can donate sulfur atoms. Magnesium oxide and to someextent the zinc oxide serve as acid scavengers picking up HBr generatedfrom the reaction of the bromine coming off the methylstyrene groups.Additional alkylene oxide can be present in the formulation beyond theamount grafted to the backbone of the polymer. Liquid EPDM polymers areadded to improve the tear strength of the composition. The oil used istypically a paraffinic or naphthenic oil as these are common toisobutylene based bladder formulation.

The polymers of modified EPDM, hydrogenated SBR modified with maleicanhydride and hydrogenated polybutadiene similarly modified with maleicanhydride subsequently reacted and grafted with polar polymers can beformulated with regular EPDM, hydrogenated SBR, hydrogenated PBD, andliquid EPDM into molded articles. Regular EPDM, hydrogenated SBR, orhydrogenated polybutadiene are from about 0 to about 98 and desirablyabout 50 to about 95 weight percent of the total rubbers used in themolded rubber articles. The modified polymers from EPDM, hydrogenatedPBD or hydrogenated SBR grafted with the polar polymers are used inamounts from about 2 to about 100, desirably about 5 to about 50 weightpercent of the total rubbery polymers used in molded articles. Stearicacid and zinc oxide act as internal lubricants for the formulation. Thisis a sulfur cured composition as there are unsaturation points in orpendant to the polymer chain. The preferred curing compounds are sulfur,sulfur donor compounds, peroxides, and sulfur cure accelerators. Thesulfur donor compounds can be di-morpholino disulfide ordipentamethylene thiuram hexasulfide or the like. The combined amountsof these curatives per 100 parts by weight of rubbers is from about 0.2to about 8, desirably from about 0.3 to about 6, and preferably about0.4 to about 5 parts by weight.

The grafting of the polar polymers to the modified EPDM, modifiedhydrogenated SBR, or modified hydrogenated polybutadiene can be doneseparately from compounding the curable compound or can be accomplishedsimultaneously with the mixing of the carbon black, silica, oil,antioxidants, zinc oxide and stearic acid, etc.

The grafting is simply the reaction of the pendant anhydride groups withthe hydroxyl group of the polar polymer to form an ester linkage.Subsequent to the grafting and homogenizing of the compound, thecurative components can be added to the compound in the mixer or on atwo roll mill.

The epichlorohydrin rubbers can be compounded into curable compoundswith curatives of the ethylene-thiourea, mercaptothio-diazole,trithiocyanuric acid type and the like. One preferred curative istrimercaptotriazine. The amount of curative is from about 0.2 to about5, and desirably from about 0.5 to about 2 parts by weight per onehundred parts by weight epichlorohydrin of rubber. The epichlorohydrinrubber can also compounded with barium carbonate, magnesium oxide,silicone oil, additional unreacted polar polymers such as polyethers,plasticizers, coumarone-indene resins and cure accelerators. Theepichlorohydrin polymers are from about 20 to about 100 weight percent,desirably about 50 to about 100 weight percent, and preferably fromabout 75 to about 100 weight percent of the rubber used in a moldedarticle.

The butadiene-acrylonitrile rubber can be compounded with typicalcompounding ingredients. A specific example is given in Table III. Thebutadiene-acrylonitrile is from about 20 to about 100 weight percent,desirably about 50 to about 100 weight percent, and preferably about 75to about 100 weight percent of the rubber used in a molded article. Theresidual weight percentages may be the optional polymers in thisspecification or the rubbers of the recipe.

The above-referenced compounded rubbery polymers (either with polarcomponents in the polymer backbone or with polar polymer grafts onhydrocarbon polymer backbones) can be formed into monomembrane curingbladders in a transfer mold. The typical procedure for molding is thatthe compound is extruded as a slug, bar, etc. The extrudate ismechanically spliced forming a ring. The ring of extrudate is put intothe transfer mold where the compound is formed into a barrel shape of acuring bladder and crosslinked. Transfer molding temperatures are340°-390° F. for 20-25 minutes with pressures of 1500 to 2000 psi.

As explained previously the rubber polymers are mixed in a Banbury orother internal mixers, or two roll mill with the fillers, plasticizers,oils, antioxidants, acid scavengers, and polar polymers untilhomogeneous. If a grafting reaction between a hydrocarbon backbone andthe polar polymers is desired, it can be accomplished during this mixingstep or prior to this step in a separate reaction.

After the initial blend is homogenous, then the curing agents are added.This is a standard compounding technique found in any basic rubbercompounding book. The mixing temperatures subsequent to adding thecuring agents are controlled to prevent premature crosslinking duringthe mixing stage. The compounded rubber stock is characterized regardingcure times by running a disc type curemeter plot at the desired curingtemperature. Additional additives such as scorch inhibitors or cureaccelerators can be added depending on the particular molding equipmentused. The physical properties reported herein are from crosslinkedmolded articles for ASTM D-412 or molded sheets prepared for the peelforce test.

The peel force test was designed to measure the adherence of a typicalsulfur cured butyl rubber tubeless tire innerliner stock cured inphysical contact under pressure to a rubber curing bladder monomembranecandidate. Two sheets, one of the experimental cured bladder candidate,the second of uncured conventional butyl rubber (polyisobutylene)tubeless tire innerliner compound, are molded for 20 minutes at 340° F.under 1000 psi pressure as a laminate. A small piece of Mylar® is usedalong one edge of the laminate between the two compounds so as to form alip of non-adhered compounds to serve as clamping points for the peeltest. After curing, the sample is removed from the press and the forceto peel the two materials from each other, bladder candidate frominnerliner compound, is measured by 180° peel test while the samples arestill hot. Typical butyl rubber curing bladder materials have peelforces of in excess of 100 pounds per inch (ppi) and the peel surface ischaracterized by cohesive failure rather than interfacial failure.Cohesive failure means the two materials are well bonded such that thefailure occurs in one of the compounds (internal tearing of thecompound) rather than at the interface between the two compounds. Thisis why a lubricant or dope is required for conventional butyl rubbercuring bladders.

When curing bladders are made from monolayer membranes of the polarpolymers or polymers with polar grafts disclosed in this specification,they have low adhesion or no adhesion to the innerliner compound whentested accordingly to the peel test. The peel force is less than 20lbs./in., desirably less than about 3 lbs./in. and preferably less than1 lbs./in. A low peel force for the purpose of this application is lessthan 3 lbs./in. It is suggested that the more polar surface of thedisclosed curing bladder compounds are less compatible with theinnerliner compound than traditional butyl rubber (isobutylene polymers)bladder and this causes less adhesion of the compounds after curing ofthe innerliner compound.

The optional interface lubricants that may be used with this inventiononly temporarily modify the surface of the bladder in that the interfacelubricants are liquids and not crosslinked to themselves or to thebladder or sleeves. These lubricants include polymeric silicones,polyols, clays, cellulose ethers, etc. which do not crosslink orchemically bind to the surface of the bladder or sleeve nor to othersuch polymers under the use and storage conditions of the bladder orsleeve.

The following examples serve to illustrate how the above listed polymerscan be compounded into useful materials having low adhesion to curing orcured hydrocarbon formulations.

                  TABLE I                                                         ______________________________________                                        EXAMPLE OF BROMINATED COPOLYMER                                               p-METHYLSTYRENE-ISOBUTYLENE                                                   REACTED WITH POLY(ETHYLENEGLYCOL)                                             Sample           A       B       C     D                                      ______________________________________                                        PEG-400          20      15      15    15                                     XP-50BR          100     85      80    60                                     EPDM Rubber      --      --      --    30                                     Liquid EPDM      --      15      20    10                                     Carbon Black (HAF)                                                                             60      60      60    60                                     Antioxidant      1       1       1     1                                      Oil              10      --      --    15                                     MgO              5       5       5     5                                      Stearic Acid     2       2       2     2                                      Eurecamide       2       2       2     2                                      Curatives                                                                     ZnO              0.75    0.75    0.75  0.75                                   Sulfur Donor     1.5     1.5     1.5   1.5                                    Physical Properties                                                           ML/4 @ 100° C.                                                                          62      77      71    58                                     Release          Yes     Yes     Yes   Yes                                    Peel Force (lbs/in)                                                                            0       0       0     3                                      Shore A Hardness 63      66      66    63                                     23° C.                                                                 Percent Compression Set                                                                        20.7    28.7    36.7  37.5                                   22 hrs 158° F.                                                         Ring Stress Strain 25° C. ASTM D412                                    100% Modulus (psi)                                                                             219     244     250   211                                    300% Modulus (psi)                                                                             1075    1026    1005  624                                    Tensile (psi)    1709    1620    1417  1241                                   % Elongation     481     496     461   617                                    Energy to break (psi)                                                                          1629    1697    1395  1795                                    Ring Stress-Strain 100° C. ASTM D412                                  100% Modulus (psi)                                                                             148     139     134   122                                    300% Modulus (psi)                                                                             672     580     554   366                                    Tensile (psi)    966     856     730   485                                    % Elongation     420     445     425   439                                    Energy to break  728     740     633   483                                    (psi)                                                                         Ring Stress-Strain after 2 days 150° C. ASTM D412                      100% Modulus (psi)                                                                             359     415     469   529                                    300% Modulus (psi)                                                                             1302    1310    1345  1429                                   Tensile (psi)    1602    1569    1403  1507                                   % Elongation     436     391     374   375                                    Energy to break  1671    1450    1328  1453                                   (psi)                                                                         Ring Tear (lbs/in)                                                                             60      77      75    59                                     ______________________________________                                         XP-50BR is a brominated pmethylstyrene-isobutylene copolymer available        from Exxon Chemical with 0.8% by wt. bromine, PEG 400 is 400 molecular        weight poly(ethylene glycol).                                                 Eurecamide is a mold release agent sold by Struktol as TR 131.           

                  TABLE II                                                        ______________________________________                                        EXAMPLE OF MALEIC ANHYDRIDE MODIFIED EPDM                                     Sample           E       F       G     H                                      ______________________________________                                        Liquid EPDM Rubber                                                                             0       0       10    0                                      EPDM Rubber      100     90      80    50                                     RT-465 (Modified --      10      10    50                                     EPDM)                                                                         Silica           20      20      20    20                                     Carbon Black HAF 30      30      30    30                                     ZnO              3       3       3     3                                      Stearic Acid     1       1       1     1                                      Oil              50      20      20    30                                     Antioxidant      1.0     1.0     1.0   1.0                                    Si69             1.5     1.5     1.5   1.5                                    PEG 8000         --      30      30    20                                     Curatives                                                                     Accelerator I    1.5     1.5     1.5   1.5                                    Sulfur Donor     2.0     2.5     2.5   3.0                                    Accelerator II   2.5     2.5     2.5   2.5                                    Physical Properties                                                           Release          No      Yes     Yes   Yes                                    Peel Force (lbs/in)                                                                            >20     <3      0     0                                      Ring Stress Strain 25° C. ASTM D412                                    100% Modulus (psi)                                                                             420     378     367   304                                    300% Modulus (psi)                                                                             1600    978     978   617                                    Tensile (psi)    3127    1764    1686  1251                                   % Elongation     545     503     496   617                                    Energy to break  3464    1865    1781  1820                                   (psi)                                                                         Ring Stress Strain 100° C. ASTM D412                                   100% Modulus (psi)                                                                             300     218     207    97                                    300% Modulus (psi)                                                                             1196    737     710   165                                    Tensile (psi)    1345    746     819   275                                    % Elongation     382     353     389   606                                    Energy to break  1050    564     669   453                                    (psi)                                                                         Ring Stress Strain. after 2 days 150° C. ASTM D412                     100% Modulus (psi)                                                                             570     541     552   421                                    300% Modulus (psi)                                                                             2527    1638    1702  895                                    Tensile (psi)    2775    2001    2049  1624                                   % Elongation     370     397     395   584                                    Energy to break  2047    1682    1733  2311                                   (psi)                                                                         ______________________________________                                         Accelerator I is Altax MBTS (benzothiazyl disulfide)                          Accelerator II is TMTD (tetramethylthiuram disulfide)                         RoyalTuf ™ 465 (RT465) is EPDM reacted with maleic anhydride to create     an EPDM backbone with succinic anhydride pendant groups. This is the          modified EPDM used as a backbone for grafting polar polymers onto. This       polymer is made and sold by Uniroyal.                                         Si69 is made by DeGussa Corp. It is                                           bis(3triethoxysilylpropyl)-tetrasulfane. It functions as a silica couplin     agent.                                                                        PEG 8000 is poly(ethylene glycol) of molecular weight 8000.              

                  TABLE III                                                       ______________________________________                                        EXAMPLE NITRILE RUBBER                                                        ______________________________________                                        Sample                  I                                                     ______________________________________                                        NBR Krynac ® 825    100                                                   Carbon Black HAF        48                                                    Stearic Acid            1                                                     ZnO                     5                                                     Castor Oil              20                                                    Heat Stabilizer         0.75                                                  Antioxidant             2                                                     Antioxidant             3                                                     CI Resin                15                                                    Curatives                                                                     Di-morpholino disulfide 1.2                                                   Pre vulcanization inhibitor                                                                           0.3                                                   Benzothiazyl disulfide  0.75                                                  Tetraethylthiuram disulfide                                                                           .80                                                   Physical Properties                                                           ML/4 @ 100° C.   33                                                    Release                 Yes                                                   Peel Force (lbs/in)     0                                                     Shore A Hardness        60                                                    23° C.                                                                 % Compression Set       24.0                                                  22 Hrs @ 158° F.                                                       Ring Stress Strain 25° C. ASTM D412                                    100% Modulus (psi)      221                                                   300% Modulus (psi)      721                                                   Tensile (psi)           3064                                                  % Elongation            841                                                   Energy to break (psi)   5007                                                  Ring Stress Strain 100° C. ASTM D412                                   100% Modulus (psi)      126                                                   300% Modulus (psi)      450                                                   Tensile (psi)           1500                                                  % Elongation            681                                                   Energy to break (psi)   2109                                                  Ring Stress Strain After Aging                                                                 2 days 121° C.                                                                     1 day 150° C.                             ______________________________________                                        100% Modulus (psi)                                                                              273        1169                                             300% Modulus (psi)                                                                             1040        --                                               Tensile (psi)    3110        1432                                             % Elongation      742        159                                              Energy to break (psi)                                                                          4819        469                                              Ring Tear @ 340° F. (lbs/in)                                                             220        220                                              ______________________________________                                         NBR Krynac ® 825 is nitrile rubber, butadieneacrylonitrile copolymer,     made by Polysar.                                                              CI resin is coumaroneindene processing resin.                                 Post vulcanization inhibitor is Santoguard PVI (Ncyclohexylthio)              phthalimide. It serves to retard scorch.                                      Heat stabilizer is Zetax.                                                

                  TABLE IV                                                        ______________________________________                                        CONTROL EXAMPLE OF BUTYL RUBBER                                               Sample               J                                                        ______________________________________                                        Butyl Rubber         95                                                       Carbon Black         48                                                       Stearic Acid         0                                                        ZnO                  8                                                        Antioxidant          0                                                        Castor Oil           8                                                        Curatives                                                                     Heat Reactive Phenolic                                                                             9.75                                                     Resin                                                                         Neoprene             5                                                        Physical Properties                                                           ML/4 @ 100° C.                                                                              75                                                       Release              No                                                       Peel Force (lbs/in)  >100 rubber failure                                      Ring Tear @ 340° F. lbs/in                                                                  220                                                      ______________________________________                                         Heat reactive phenolic resin is actually added with the carbon black and      other ingredients before the final curative, which is neoprene rubber.        Neoprene rubber serves to activate the cure system.                      

                  TABLE V                                                         ______________________________________                                        EXAMPLES EPICHLOROHYDRIN RUBBER                                               Sample       K       L       M     N     O                                    ______________________________________                                        Hydrin ™  100     100     100   100   70                                   SAN/EPDM     0       0       0     0     30                                   BaCO.sub.3   4       4       4     0     4                                    MgO          0       0       0     4     0                                    Black HAF    48      48      48    48    48                                   Antioxidant  1       1       1     1     1                                    Antioxidant  0.4     0.4     0.4   0.4   0.4                                  Silicone Oil 5       5       5     5     5                                    CI Resin     8       8       8     8     8                                    Dioctyl Sebacate                                                                           5       5       5     5     5                                    Plasticizer                                                                   Curatives                                                                     Accelerator III                                                                            1.0     1.0     1.0   1.0   1.0                                  Trimercaptotriazine                                                                        1.0     1.25    1.5   1.0   1.0                                  Physical Properties                                                           ML/4 @ 100° C.                                                                      44      41      42    34    68                                   Release      Yes     Yes     Yes   Yes   Yes                                  Peel Force (lbs/in)                                                                        0       0       0     0     0                                    Shore A Hardness                                                                           71      71      73    70    82                                   23° C.                                                                 Compression Set %                                                                          18.4    16.0    16.7  12.0  24.8                                 22 hrs 158° F.                                                         Ring Stress Strain ASTM 25° C. D412                                    100%         436     483     405   409   655                                  300%         1473    1436    1208  1319  1488                                 Tensile (psi)                                                                              1835    1696    1485  1685  1523                                 % Elongation 494     459     488   505   379                                  Energy to break                                                                            2407    2102    1943  2268  1635                                 (psi)                                                                         Ring Stress Strain 100° C. ASTM D-412                                  100% Modulus (psi)                                                                         336     331     347   310   309                                  Tensile (psi)                                                                              1057    1012    981   960   861                                  % Elongation 323     321     312   320   336                                  Ring Stress Strain After 2 days 150° C.                                100% Modulus (psi)                                                                         605     881     975   794   1442                                 Tensile (psi)                                                                              914     1232    1202  1158  1514                                 % Elongation 250     210     182   234   150                                  Energy to break                                                                            742     805     665   752   574                                  (psi)                                                                         ______________________________________                                         Hydrin ™ is Epichlorohydrin rubber from Nippon Zeon. This one is a         homopolymer of epichlorohydrin rather than a copolymer.                       SAN/EPDM is a graft of SAN onto EPDM. It is Royaltuf ™ 372 available       from Uniroyal.                                                                BaCO.sub.3 is a blend of predominantly BaCO.sub.3 masterbatched in rubber     CI Resin is coumaroneindene processing resin. Accelerator III is Rhenofit     a mixture of urea and sulfamic acid bonded to silica.                    

The examples A, B, C, and D of Table I using a brominated copolymer ofp-methylstyrene-isobutylene reacted with poly(ethylene glycol) showedgood release (lbs/in peel force) in the Peel Force Test at two differentconcentrations of PEG-400 (poly(ethylene glycol)). Examples B, C, and Dshow the substitution of EPDM and liquid EPDM for the XP-50BR stillgives good release properties. The example compounds show good retentionof physical properties even after heat aging. Thus, the grafted polarunits have not significantly affected the physicals while theysignificantly enhanced the release.

The example of maleic anhydride modified EPDM (Table II) showed thatSample E, a compound without the polar polymer grafted onto the maleicanhydride modified EPDM did not release from the butyl rubber innerlinermaterial in the peel test. The measured peel force was in excess of 20lbs/inch of peel interface. Samples with the polar PEG-8000 grafted ontothe modified EPDM (Samples F, G, and H) showed release and peel forcesof less than 3 lbs/in. Samples G and H showed good physical propertiesfor this application and good heat aging characteristics.

Sample I of nitrile rubber (Table III) showed excellent release and noadhesion in the peel test. The physical properties and heat aging areacceptable up to 120° C.

The control sample J of butyl rubber (Table IV) without any polarpolymers or polar polymers grafted to hydrocarbon polymer backbonesshowed no release from a butyl rubber innerliner in the peel force test.The peel force was in excess of 100 lbs/in and showed tearing in therubber rather than at the interface between the two compounds.

The samples K-0 of epichlorohydrin rubber (Table V) showed release inpeel force test. They had approximately 0 lbs/in peel force. Example 0showed that blends of Hydrin™ rubber with SAN/EPDM also give goodrelease properties and low peel force. The physical properties of thesepolymers were in the range necessary for curing bladders.

The utility of these disclosed polymers, copolymers, and graftcopolymers having low adhesion to hydrocarbon rubbers like butyl rubberinnerliners is to make curing bladders, sleeves, or other shaped polymerproducts especially those shaped products to be used in molding, shapingand curing hydrocarbon rubber compounds. The disclosed polymers have lowadhesion to the cured hydrocarbon rubbers saving the necessity ofapplying lubricants to the interface between the molding device (such asa curing bladder) and the hydrocarbon rubber compound to be cured. Theyalso eliminate the need for applying surface layers (i.e. makinglaminates) of polymers such as crosslinkable polysiloxanes orpolyurethanes. They also eliminate the need for chemically attachedpolysiloxane polymers. These polysiloxane polymers are attached via areaction of unsaturation present on the polysiloxane. This technology istaught by U.S. Pat. No. 4,710,541, which is hereby incorporated byreference. The shaped articles and curing bladders or sleeves disclosedare useful in assembling, forming, and curing hydrocarbon based rubbermaterials.

While in accordance with the Patent Statutes, the best mode andpreferred embodiment has been set forth, the scope of the invention isnot limited thereto, but rather by the scope of the attached claims.

What is claimed is:
 1. In a curing press for hydrocarbon based rubbers of the type which uses an inflatable bladder or sleevewherein the bladder or sleeve has: an ultimate tensile strength of 1500 psi or more and a 300 percent modulus of 500-1000 psi, wherein said bladder or sleeve retains a capability to achieve 300 percent elongation after 48 hours at 121° C., and wherein said bladder or sleeve has surfaces having crosslinked polymers therein, the improvement wherein said crosslinked polymers before crosslinking comprise: a reaction product comprising(a) a rubber selected from at least an ethylene propylene terpolymer, substantially hydrogenated polybutadiene, or substantially hydrogenated styrene-butadiene rubber, and (b) maleic anhydride and which reaction product is melt blended with a polar polymer under shear at temperatures from about 90° C. to about 220° C.; wherein said polar polymer is at least one polymer or copolymer of polyether, polyester, or polycarbonate from the reaction of phosgene with glycols having from about 1 to about 4 carbon atoms wherein said polar polymer is from about 2 to about 40 weight percent of the total rubbers in said bladder or sleeve.
 2. In a curing press according to claim 1, wherein said rubber comprises an ethylene-propylene terpolymer.
 3. In a curing press according to claim 2, wherein the amount of said maleic anhydride is from about 1 to about 20 parts by weight per one hundred parts by weight of said rubber, and wherein the amount of said polar polymer is from about 5 to about 30 weight percent based upon the total of said polar polymer and said reaction product.
 4. In a curing press according to claim 1, wherein said rubber comprises a polybutadiene hydrogenated to remove from about 90 to about 99.5 percent of the unsaturation.
 5. In a curing press according to claim 4, wherein the amount of said maleic anhydride is from about 1 to about 20 parts by weight per one hundred parts by weight of said rubber, and wherein the amount of said polar polymer is from about 5 to about 30 weight percent based upon said polar polymer and said reaction product.
 6. In a curing press according to claim 1, wherein said rubber comprises a styrene-butadiene rubber hydrogenated to remove from about 90 to about 99.5 percent of the unsaturation.
 7. In a curing press according to claim 6, wherein the amount of said maleic anhydride is from about 1 to about 20 parts by weight per one hundred parts by weight of said rubber, and wherein the amount of said polar polymer is from about 5 to about 30 weight percent based upon the total of said polar polymer and said reaction product.
 8. In a curing press according to claim 1, wherein said polar polymer is one or more polyethers polymerized from ethylene oxide, propylene oxide, tetramethylene oxide, or combinations thereof.
 9. In a curing press according to claim 1, wherein said polar polymers are polyesters polymerized from cyclic lactones.
 10. In a curing press according to claim 8, wherein said polar polymer is from about 5 to about 30 weight percent of the total of said reaction product and said polar polymer.
 11. In a curing press according to claim 9, wherein said polar polymer is from about 5 to about 30 weight percent of the total of said reaction product and said polar polymer.
 12. In a curing press according to claim 10, further comprising a liquid interface lubricant on said bladder or sleeve.
 13. In a curing press for hydrocarbon based rubbers including a vulcanized monolayer curing bladder or sleeve having its entirety comprised of a single crosslinked elastomeric composition, wherein the bladder or sleeve retains its elasticity to 300 percent elongation for at least 48 hours at 121° C., the improvement wherein the elastomeric composition before curing comprises:a reaction product comprising(a) a rubber of ethylene propylene terpolymer, substantially hydrogenated polybutadiene, or substantially hydrogenated styrene-butadiene rubber, with (b) maleic anhydride and which reaction product is melt blended with a polar polymer under shear at temperatures from about 90° C. to about 220° C.; wherein said polar polymer is at least one polymer or copolymer of polyether, polyester, or polycarbonate from the reaction of phosgene with glycols having from about 1 to about 4 carbon atoms wherein said polymer is from about 2 to about 40 weight percent of the total rubbers of said curing bladder or sleeve.
 14. In a curing press according to claim 13, wherein the amount of said maleic anhydride is from about 1 to about 20 parts by weight per 100 parts by weight of said rubber and wherein the amount of said polar polymer is from about 5 to about 30 weight percent based upon the total of said polar polymer and said reaction product.
 15. In a curing press according to claim 14, wherein the reaction of said rubber with maleic anhydride is conducted at a temperature from about 50° to about 180° C. for a period of time from about 0.1 to about 24 hours with from about 0.01 to about 5 parts by weight free radical initiator per 100 parts by weight of said rubber.
 16. In a curing press according to claim 15, wherein said rubber is an ethylene-propylene terpolymer.
 17. In a curing press according to claim 15, wherein said rubber comprises a polybutadiene hydrogenated to remove from about 90 to about 99.5 percent of the unsaturation.
 18. In a curing press according to claim 15, wherein said rubber comprises a styrene-butadiene rubber hydrogenated to remove from about 90 to about 95 percent of the unsaturation.
 19. In a curing press according to claim 15, wherein said polar polymer comprises one or more polyethers polymerized from ethylene oxide, propylene oxide, tetramethylene oxide, or combinations thereof.
 20. An inflatable curing bladder or sleeve for use in vulcanizing and molding hydrocarbon materials comprising;a bladder or sleeve having at least one exterior surface exhibiting low adhesion with said hydrocarbon materials after vulcanization of said hydrocarbon materials, said bladder or sleeve, and said at least one exterior surface of said bladder or sleeve comprising the reaction product of one or more of rubbers selected from ethylene-propylene terpolymer, substantially hydrogenated polybutadiene, and substantially hydrogenated styrene-butadiene copolymer rubber reacted with maleic anhydride and subsequently melt blended with from about 2 to about 100 parts by weight polar polymers per 100 parts by weight of said one or more rubbers.
 21. An inflatable curing bladder or sleeve according to claim 20, wherein said bladder or sleeve comprises said reaction product of melt blending of one or more brominated p-methyl-styrene-isobutylene copolymers with one or more polar polymerswherein said one or more polar polymers comprise at least one polymer or copolymer of polyether, polyester or polycarbonate from the reaction of phosgene with glycols having from about 1 to about 4 carbon atoms, and wherein said one or more polar polymers are from about 2 to about 40 weight percent of the total rubbers in said bladder or sleeve.
 22. An inflatable curing bladder or sleeve according to claim 21, wherein said polyethers have from 1 to 4 carbon atoms per repeat unit and said polyester is from the ring opening polymerization of cyclic lactones having from 4 to 5 carbon atoms and wherein said one or more polar polymers are from about 2 to about 40 weight percent of the total rubbers in said bladder or sleeve.
 23. An inflatable curing bladder or sleeve according to claim 22, wherein said reaction product comprises graft copolymer having grafts of said one or more polar polymer and a backbone of p-methylstyrene-isobutylene copolymer. 